Problem: Solve for $x$ : $x - 21 = 1$
Add $21$ to both sides: $ \begin{eqnarray} \\ x - 21 &=& 1 \\ \\ {+21} && {+21} \end{eqnarray} $ $ \begin{eqnarray} \hphantom{-21 + x} &\hphantom{=}& \hphantom{1} \\ x &=& 1 {+ 21} \\ \end{eqnarray} $ Simplify. $ x = 22$